A1200 developed a brown hue/kickstart suddenly

[MrMila]

Hey everyone, new to the forum so I'll do my best. I'm 37 from London, photographer, Amiga fan when I was a kid in the 80's 90's

This is a multi problem/question thread I think so I'll explain as thoroughly as I can. I have added some photo links below, I'm not a huge forum user so I think I have used the right format. Medium thumbnails but they are linked and should take you to the high res versions. I have more photos and angle if they help?



I'm an old school Amiga head but know nothing of the scene in regards to the machines these days so please forgive nay wrong terms and names.

I just dug out my old A1200 from my mums loft as my kids enjoyed playing a few Amiga games on the Raspberry Pi and I figured I would see if the real thing works.



Opened it up, cleaned out all the dust and fluff etc.

Plugged it into a TV using an Amiga scart cable. I guess that's the RGB.


The machine powered up fine!!!! Purple workbench screen, drive chugging away. Managed to get a bunch of old disks up and running and they seen to play fine and the audio is there.



There is vertical banding running down the screen but pretty faint.


I noticed that around the sprites I could see some kind of haze/distortion when moving. Best description would be like heat haze around it. Again, it's been sooooo long since I've played on an Amiga I don't really have a bench mark to go from regarding what is normal.



We had the machine running last night for about 20 minutes playing Push Over when suddenly there was a shift in colour across the whole screen. Everything took on a yellow/brownish hue.


When I rebooted the Amiga the purple Workbench screen was now a muddy shade of redish brown. There where a few flickers of purple once in a while but now it is permanent brown.


Colours on all games take on a hue now.
I have also noticed that there are odd little graphic glitches here and there on loading games. Little bits of things missing sometimes or just looking scrambled. Not sure if it's linked.

I have tried plugging in to another tv with a composite cable and that looks terrible as well although not brown, more washed out blue maybe.
I don't have another cable to test and don't have an RF cable at the mo.



I was thinking of having it recapped as i presume it will need it having sat in the loft for so long so had the whole machine open again.



I have taken very high res photos of the boards but notices that it seems to have been repaired before, probably when we were kids.

There are two yellow wires that have been used to bridge some chip pins, guessing to repair bad track or something.

Do those look normal and should they be touching two pins at one end in on case?





Also I could be wrong but there looks like there is a cap or two missing but is that something to do with timing?





I have tried flexing the board a little while running and the picture does not change. I've pressed a few chips lightly and various other things. Nothing seems to make the picture flicker or suggest something loose.


So, Any ideas? I want to figure it out so if something needs doing I can have it done at the same time as the recap.


Hope that all makes sense. Please tell me if I need to change image links etc

[Vypr]

The yellow wires would have been installed at the factory, you have a fairly early revision board there (1B), morecommonly you'll see 2B and 1D4 revisions. I had a 1B board with the same yellow wire.

Don't worry about the missing caps, it is quite normal for some caps not to be installed as they were not needed.
I would look at getting it recapped though, it looks like there may have been some leakage, especially around C236, C237 and C214 the solder pads look very dull which can be a sign of leakage. Since these caps handle video signal they could be the cause of the video issues

[Daedalus]

Well, the capacitors failing themselves wouldn't cause the colour fault, but leakage from them can and does damage the video circuitry nearby, resulting in video problems. It looks like you're missing a certain portion of the blue signal, so it's possibly a high blue bit missing, or some other similar issue.

You're connecting it with SCART to the TV, but are you connecting the cable to the Amiga using the 3 phono plugs (red, white and yellow), or to the RGB port (red & white phono plus 23-pin D plug)? Colour issues can be introduced to composite more easily by leakage on the board, so you might find that the RGB still works fine if you're using the yellow phono connection for video.

Either way, I would say get it to someone for repair and replacement of the capacitors. Preferably sooner rather than later, because if the damage is caused by capacitor leakage, it's only going to get worse with time. But the fault should only be minor.

As for the ghosting around sprites, that's not normal as such from the Amiga's perspective, but is probably a side-effect of the TV's upscaling and processing of the image. If the TV has a game mode, that might help reduce the effect.

[MrMila]

Wow, didn't think the wires would have been a factory standard. Interesting.

I'm connecting via the RBG port with the red/white and 23 pin cable.

Was planning to get it sent off asap but this Corona nightmare has currently wiped my work diary out so not sure I can justify the expense at the mo. But I will have a think and see if I can as I wanna get stuck into some gaming!
I have found a list or two of people but any recommendation for someone near to London or UK based who is well priced?

[Daedalus]

Yeah, then I strongly suspect one or more of the blue bits between Lisa and the DAC are having issues, or maybe the DAC itself. I have a list of a few recommended Amiga repairers, but none in London. I vaguely remember someone recommending someone in London though, so there is someone, somewhere

[Gordon]

If you remove the video and sound caps, will you still get sound and picture if you have a good PSU?

[Daedalus]

It depends on the capacitors. Most of them, yes, you will. But there are a couple of capacitors that are used for coupling the audio output. If you remove them, you'll get no sound. There aren't really equivalents like that in the video circuitry, with the exception of C236 and 237 which couple the RF and composite signals. C237 is for composite, but is a through hole capacitor and less likely than the SMT ones to die, and neither of them will affect the RGB output.